>> the nutrition science initiative. we went back and looked at every scientific study back to world war ii that attempted to answer that equipment think gary we found 82 studies that had attempted to answer that but they were all fraught with the same sort of limitations and problems. so in 2012 we actually don't know the answer to that question base opened rigorous science, although that's plenty of anecdotal evidence to suggest that a calorie is not a calorie. >> one thing i know that is absolutely must be true is you should eat less fat. fat does all this harm. and yet you eat lots of fat. and you're a doctor. stanford doctor. what's that about? >> well, like i said, three or four years ago when i got the point where i was too overweight to handle my own existence and my wife said i needed to be a little less not then, i realized i probably had a co-bow hydrate intolerance issue and all those whole grains and things i was eating were leading to me becoming fatter and i realized if i stripped that stuff out of my diet